Organic solvents such as perchloroethylene and other low-pressure liquid solvents have long been popular for use in cleaning systems such as dry cleaning systems. As illustrated in FIG. 1, a dry cleaning facility employing these systems typically receives solvent and detergent from a supplier or suppliers, and garments or other articles to be cleaned from customers. Garments are returned to the customers, and some solvent escapes to the atmosphere. Lint, filter media, and other still residue (from the distillation of solvent on site) are classified as a hazardous waste and should be disposed of accordingly.
Recently, however, there are growing concerns that these solvents and by products may harm the environment and pose occupational safety hazards. These concerns have led to an extensive search for alternative solvents that are less hazardous and systems for applying such solvents. Some of this research has focused on systems utilizing solvents that are gases at low pressure. These systems may operate either under subcritical conditions such that the solvent is present as a liquid or under supercritical conditions such that the solvent is present as a supercritical fluid. Some of these systems utilize liquid carbon dioxide (CO.sub.2) as a cleaning solvent.
One such carbon dioxide cleaning system is known as the Drywash.TM. system, illustrated in FIG. 2 herein. This system was developed by Hughes Environmental and Global Technologies Inc. In the Drywash.TM. dry cleaning system, the carbon dioxide is premixed with the necessary detergent formulations and shipped to the customer in bulk form. This approach is cumbersome because it requires shipping large volumes of detergent formulation, tends to increase the cost of the ingredients to the end user, does not permit the cleaning facility to utilize existing carbon dioxide distribution infrastructure, and is not conducive to franchising individual owners of dry cleaning facilities (which would facilitate widespread usage of the technology).
Accordingly, there is a need for alternative processes for implementing carbon dioxide dry cleaning techniques.